Process for the treatment of egg whites



' tionable odor and flavor.

Patented Feb. 12, 1952 PROCESS FOR THE TREATMENT OF EGG WHITES Arthur M. Kaplan, Hyattsville, Md., and Mathilde Solowey, Washington, D. 0., assignors to the United States of America as represented by the Secretary of Agriculture No Drawing. Application May 22, 1950, Serial No. 163,574

14 Claims. (01. 99-113) (Granted under the act of March 3, 1883, as

amended April 30, 1928; 3'70 0. G. 757) This application is made under the act of March 3, 1883, as amended by the act of April 30, 1928, and the invention herein described, if patented in any country, may be manufactured and used by or for the Government of the United States of America for governmental purposes throughout the world without the payment to us of any royalty thereon.'

This application is a continuation in part of our copending application Serial No. 126,261 filed November 8, 1949, the disclosure of which is incorporated herein by reference.

This invention relates to the manufacture of dried egg whites, and more particularly to methods of thinning liquid egg white and of removal of sugar components thereof by nonproliferating cell fermentation.

In the production of commercial dried egg whites, that is, dried egg albumen, it is common practice to thin liquid egg white by fermentation with microorganisms either naturally present therein or introduced by inoculation with suitable microbiological cultures. The activity of these microorganism in the course of the fermentation process causes elimination of the sugar present in the egg white and results in a separation of the insoluble constituents from the liquid albumen fraction, which can then be readily segregated for subsequent processing and drying.

The yield as well as the quality of dried egg albumen derived from egg whites thinned by natural fermentation very greatly, and the products so obtained frequently possess an objec- Egg whites subjected to controlled fermentation also tend to yield dried egg albumen of varying quality due to contamination of the mother cultures used as inocula, or to the failure to suppress in the course of the fermentation the detrimental action of deleterious microorganisms accidentally present in the egg white, since generally in the fermentation of egg whites by previously proposed procedures the number of microorganisms initially present therein, as well as of those added by inoculation, increases as the sugar is utilized and fermentation proceeds to completion. It has also been found that under certain conditions addition of starter cultures induces a stimulated growth of microorganism accidentally present in the egg white which frequently causes the development of objectionable odors and flavors.

By increasing the size of the inoculum, when using any suitable microorganisms capable of producing acid from sugar, it is possible to decrease the length of time necessary to bring the fermentation process to completion from the usual 48-72 hours to a period of about 21-24 hours. However, under these conditions also, the detrimental activity of microorganisms initially present in the egg white is not always impeded. Furthermore, the preparation of starter or -mother culturesis a laborious, time consuming and exacting task, and since it is impracticable to prepare pure mother cultures of liquid egg white on a large scale under commercial conditions, the use of large inocula results in adulteration of the fermented egg whites with the other media used to culture the microorganisms that brin about the fermentation.

We have found that the disadvantages inherent in the methods heretofore proposed are 7 obviated and complete fermentation of egg whites is rapidly attained on effecting the process by means of microorganisms capable of producing acid from sugar, added as an inoculum in a nonproliferating stage.

According to the method of our invention, a concentrated microbial preparation of microorganisms capable of producing acid from sugar, such as Lactobacilli, streptococci and Aerobacter is prepared by growing the organisms in a suitable liquid medium under optimum growing conditions and then recovering the microbial cells from the culture by any suitable procedure such as filtration or centrifugation. The resulting concentrated microbial preparations, as harvested, or in the form of suitable pastes, slurries or suspensions, are used as inocula for direct seeding of the egg whites to be fermented with desired concentration of the organisms, allowing the fermentation to proceed to completion under optimum conditions of pH, aeration and temperature, as required by the specific microorganisms employed.

We have found that on following this procedure complete fermentation is attained within a very short period, with no proliferation of the organisms introduced as an inoculum or of any organisms accidentally present in the egg white.

We have further found that certain acid-forming microorganisms, such as Steptococcus lactis which, when used in the form of broth culture inocula either do not ferment egg white or cause only a partial reduction of the sugar content thereof on prolonged incubation, are eminently well-adapted for use in accordance with the method of our invention and bring about a rapid and substantially complete fermentation of the reducing sugar of egg white over a relatively wide range of fermentation temperature and pH.

Upon completion of the fermentation as determined by the usual chemical tests. the inother appropriate procedure and the fermented egg whites dried in a conventional manner. Our fermentation method causes no breakdown of the egg white protein by proteolysis, and since any microorganisms that may be accidentally present in the egg white do not multiply in the course of the fermentation process, the fermented liquid egg whites and the dried albumen obtained therefrom are free from objectionable off-flavor and odor. The final products thus obtained undergo no browning on subsequent storage at ordinary and elevated temperatures, while their appearance and properties are characteristic of the finest grade of edible dried egg albumen.

In the preparation of concentrated microbial preparations used as inocula in our process, the harvested cells can be utilized in the form of pastes, slurries or suspensions by combining them with liquid egg white, water, or any other nontoxic liquid which will not adulterate the egg whites or be harmful to the microorganisms. Such preparations can be stored until needed since we have found that they can be maintained at refrigerator temperatures for long periods with The experimental data shown in Table 1 indicate that the fermentation process for the sample inoculated with the broth culture did not cause a depletion of the sugar in 72 hours, whereas the EXAMPLE II no significant decrease in viability. Thus our six 200 milliliter portions of liquid egg white method obviates the necessity of constantly prewere used Two of these portions were adjusted parmg mother cultures of fermemfmg F wmte' to pH 7.0, two were adjusted to pH 7.5, while the and the hazards of contamination 1nc1dental remaining two portions were left unadjusted at F also precludes adltlteraum of egg pH 9.0. These samples were inoculated each whites with extraneous materlals such as are with 1 percent by weight of concentrated Strep Present m culture medla' 9 fermentmg grams tococcus lactis cells, harvested as described in vegetable masses used as lnocula. Furthermore, Example I. added as a dispersion in an equal the concentrated microbial preparations utilized volume of 035 percent saline The inoculated as inocula in our process make it possible to seed H samples were divided into two Sets each the egg whites with concentratlons of l'nlCIO- 3o prising three samples of initial pH 7.0, and organisms that cannot be attained by using ordi respectively one set was incubated at nary starter or mother cultures. 26-28 C. and the other at 37 C. The course The fol w n examples Illustrate the of fermentation was followed by making sugar tion. 40 and pH determinations at suitable intervals. The EXAMPLE 1 results so obtained shown in Table 2 indicate that the fermentation was essentially complete Two milliliter portions of liquid egg white within 2-4 hours under all conditions of incubavere adjusted to pH 6.7-6.8 with 1N lactic acid. tion temperature and initial pH employed.

Table 2 Course oli'ermcnlation Incubation 'lime, Initial pH 7.0 initial 111! 7.50 initial pli 9.00 Temperature Hours 1 i pH Glucose, i pll Glucose, l p11 Glucose, I i percent I percent percent l 0 7.00% .339i150 .001 0.00 .311 1 0.401 .221 7.00} .zos soa .au 26-28 2 0.0o| .100 0.10, .104l1s0 .000 l a 5.00 .024 5.051 .00.= 0.00 .020 4 0.50 .008 l 0 7.00 .311 7.50. .:4s1.9.00- .055 C 1 6.30 k .147 0.:10 .1011 7.1:. .103 "1 '2 5.60 .oo5 1 0.00 .ou5 3 0.00 l .005 3 5.60 i Jkl-l I 6.00 i .005 i l 1005 L l I One of these samples was inoculated with approximately 3 percent by weight on the basis of the liquid egg white, of a twenty-four hour broth culture of Streptococcus lactz's (containing on the order of 3.0)(10 organisms per milliliter). The other sample was inoculated with 1 percent by weight of a concentrated cell preparation obtained by centrifugation of 24 hour broth cultures of Streptococcus lactis using a Sharples Super Centrifuge, and containing on the order of 4.0)(10 organisms per milliliter of packed cells. The samples were incubated at 37 C. and sugar and pH determinations made at suitable intervals.

EXAMPLE III Seven liters of unadjusted egg white were ins oculated with 78 grams of concentrated Streptocoocus lactis cells, obtained as described in Ex ample I, and incubated at 37 C. Sugar, pH, nonprotein nitrogen (Hawk, Oser and Summerson: Practical Physiological Chemistry 12th ed., Blakiston 81 Co., Philadelphia, 1947) and formol nitrogen determinations were made at suitable intervals. The data shown in Table 3 indicate that no significant proteolysis occurred during the fermentation which was essentially complete within 2 hours.

Table 3 I H H I Glucose, N. P. N.. mgm. Formol Nitrogen, p I percent percent mgm. crcert 9.0 Q .334 6. 48 74.13 6.7 l. .057 6.8 I .013 13.50 90.09

EXAMPLE IV Table 4 g I Bacterial count. Glucose. hour I per milliliter percent "I 5.0 X 8.60 .320 1 5.0)(10' 6.30 .066 1.5 "I 5.0 X 10 6. 20 .006

Similar results were obtained by analogous procedures on conducting the fermentation with concentrated Streptococcus lactis preparations, essentially as described in the foregoing examples, at temperatures from about 21 to about 37 C., usin either unadjusted liquid egg white, or egg white acidified to an initial pH value up to about 6.7, either with lactic acid or with any other suitable acidifying agent such as hydrochloric, tartaric, or citric acid. The concentrated microbial cells preparation, which may contain, for example, on the order of l.0 10 to 1.0 10 organisms per gram of concentrate, can also be recovered from broth cultures by filtration as described by Kaplan et al. (1946, J. Bact. 52, 513-517) and used as inocula either as such or admixed with liquid egg white, water, saline or any other nontoxic liquid in concentrations such as to give on inoculation a product containing on the order of 1.0 10 microorganisms per milliliter.

on the basis of the foregoing examples, it can be seen that through the use of our process a fermented egg white can be produced, using Streptococcus lactis in a non-proliferating state, having a pH range of 5.6-6.6 as desired. The final pH of the product varies with the initial pH thus enabling a product to be produced at varying pH values suitable for specific purposes. Thus, if a dried *eggalbumen is desired suitable for use in baking an angel food cake, or if a dried albumen is desired with a pH near neutrality, it is not necessary to adjust the pH of the egg white prior to fermentation and the fermentation can be carried out simply by inoculating the concentrated microbial suspension, slurry or paste di-' rectly into the unadjusted egg white.

Angel food cakes baked using dried egg albumen. produced from egg white fermented by Streptococcus lactis according to our process, have all the attributes of the finest qualities desired in such baked produc We claim:

l. The method of fermenting liquid 688 White by Streptococcus lactis, said microorganism being in a non-proliferating stage during the fermentation process.

2. The method of eliminating substantially all the sugar present in egg white which comprises subjecting liquid egg white to non-proliferating cell fermentation by Streptococcus lactis.

3. The method of fermenting liquid egg white which comprises inoculating the egg white with a concentrated cell preparation of Streptococcus lactis in an amount sufilcient to cause on subsequent incubation of the inoculated material a substantially complete utilization of the sugar content of egg white by the microorganism of the inoculum in a non-proliferating stage.

4. The process comprising cultivating Streptococcus lactis in a liquid medium, recovering the microbial cells from the resulting culture in the form of a concentrate, inoculating liquid egg white with the concentrate and allowing the inoculated egg white to'undergo non-proliferating cell fermentation.

5. The process of claim 4 wherein the liquid egg white is inoculated at a pH within the range from 6.7 to about 9.0.

6. The process of claim 4 wherein the inoculation of the liquid egg white is eifected by addition of microbial cells of Streptococcus lactis in admixture with a nontoxic liquid.

'7. A process comprising cultivating Streptococcus Zactis in a liquid medium, recovering the microbial cells from the resulting culture in the concentrate containing on the order of 1.0x 10 to 1.0)(10 organisms per gram of the concentrate and inoculating liquid egg white with the organisms thus obtained in an amount sufficient to give an inoculated product containing on the order of 1.0)(10 microorganisms per milliliter.

8. The process of claim 7 wherein egg white is inoculated by addition of the microbial cells in admixture with a nontoxic liquid of the group consisting of liquid egg white, water and saline.

9. The process of claim 8 wherein inoculation is effected by addition of the microbial cells in admixture with saline.

10. The process which comprises inoculating liquid egg white with a concentrated microbial cell preparation of Streptococcus lactis in an amount sufiicient to give an inoculated product containing on the order of 1.0X10 microorganisms per milliliter of egg white and maintaining the inoculated egg white at a temperature of about 21-37 C. until the glucose content thereof is reduced to at least about 0.018 percent by weight.

11. The process of claim 10 wherein the initial pH of liquid egg white is adjusted to 6.7-7.5.

12. The process of claim 10 wherein the initial pH of the liquid egg white is adlusted to 7.5-8.6.

13. The process of claim 10 wherein the liquid egg white is inoculated at its natural pH.

14. The process of claim 10 wherein the inoculated egg white is maintained at a temperature 'of 21-37 C. for a length of time sumcient to ,reduce its glucose content to at least 0.005 percent by weight.

' ARTHUR M. KAPLAN.

MATHILDE SOLOWEY. REFERENCES crrcn The following references are of record in the file of this patent:

the liquid 4 

1. THE METHOD OF FERMENTING LIQUID EGG WHITE BY STREPTOCOCCUS LACTIS, SAID MICROORGANISM BEING IN A NON-PROLIFERATING STAGE DURING THE FERMENTATION PROCESS. 